Difference Between Hashtable and Dictionary in C#

However, there are some key differences in how they operate and when to use each one.

Creating and Adding Elements to a Hashtable

A Hashtable can be used to store key-value pairs without specifying the type of key or value. The following example demonstrates how to create a Hashtable and add some elements to it:

Hashtable studentGrades = new Hashtable();
studentGrades.Add(101, "A"); // Adding key/value pair using Add() method
studentGrades.Add(102, "B");
studentGrades.Add(103, "C");

// The following line will throw a runtime exception because the key already exists
// studentGrades.Add(103, "A");

foreach (DictionaryEntry entry in studentGrades)
{
    Console.WriteLine("Student ID: {0}, Grade: {1}", entry.Key, entry.Value);
}

In this example, the Hashtable stores student IDs as keys and their corresponding grades as values.

Creating and Adding Elements to a Dictionary

A Dictionary<TKey, TValue> is a generic collection that requires you to specify the types of both the key and the value.

Dictionary<int, string> studentGrades = new Dictionary<int, string>();
studentGrades.Add(101, "A"); // Adding key/value pair using Add() method
studentGrades.Add(102, "B");
studentGrades.Add(103, "C");

// The following line will throw a runtime exception because the key already exists
// studentGrades.Add(103, "A");

foreach (KeyValuePair<int, string> pair in studentGrades)
{
    Console.WriteLine("Student ID: {0}, Grade: {1}", pair.Key, pair.Value);
}

In this case, the Dictionary stores student IDs as integers and their grades as strings.

Hashtable vs Dictionary

Below is a comparison table highlighting the differences between Hashtable and Dictionary:

In conclusion, while both Hashtable and Dictionary are used for storing key-value pairs, Dictionary is generally the preferred choice due to its better performance, type safety, and support for generic types.